Radio direction finding apparatus



March 18, 1952 R. c. SABINS 2,589,578

RADIO DIRECTION FINDING APPARATUS Filed April 15, 1946 -3 Sheets-Sheet 1 INVENTOR. 201.: AND C. '5'A B A 5 @wrw A TTOENEYS -March 18, 1952 R sABlNS RAD-Io DIRECTION FINDING APPARATUS Filed April 15, 1946 3 Sheets-Sheet 2 INVENTOR. ND 6. 5A 5/A/6 ATT'OEA/SVS March 18, 1952 R. c. SABINS 2,589,578

RADIO DIRECTION FINDING APPARATUS Filed April 15, 1946 3 Sheets-Sheet 5 INVENTOR. PQlZAA/D 0. SAE/A/S Patented Mar. 18, 1952 UNITED STATES PATENT OFFICE Application April 15 1946 Serial:No. 662,123 "7 Claims. (01.""34-3-415) Direction finding radio equipment has been 7, utilized on ships andairplanes hereto'foregbut the loop or radio directive antenna of .such .equipment has been oriented with the .craft, such asa ship or an airplane, sothatit was nota true di rectionfinder, but rathergave a -reading of the angle between the center Aline of the craft and the direction from it of the radio station'located by the direction finder. .It-has'been customaryto; determine the heading ofaship at thelsame'time that .the radio station directionreading is taken,

and fromsuch direction and the'heading to3compute the actual bearing of the radio station.-

From two or more such bearings a fix o'f the crafts positionmay beobtained.

It is the principal objector myinvention coordinate the directionfinding equipment with 1 the crafts navigational compass, which is "basie cally an accurate instrument, and is compen sated for errors, so that a direct reading 'ofthe" radio station bearing from the craft can be .obtained irrespective of its heading or change of heading, subject only to correction for the mag netic declination at the particular location of the craft.

It is especially an object to coordinate the radio direction finding equipment with the navigational compass of the craft by asimple position arrangement of such compass and the "loop an tenna of the. direction finding radio "I'BCBlVGIiIO- tatable about .an upright axis. Specifically'thei rotative axis of the antenna'is "aligned withtlr bearing or rotative axis of the compass card.

Not only is the position of the radio loop "an tenna oriented with respect to "the craft,s'navigational compass, but the attitude indicating mechanism'for the antenna defines an 'index which cooperates with -such compass in deter mining the bearing of a radio station, and may also be arranged to serve as the normal craft heading index or lubbers line for the craffls compass. Another object of my invention is to accomplish the results described above by the use of simplemechanism. Other advantages of my direction finding equipment will be discussed inithe following description of q representative forms of mechanism.

Figure .1 is a rear elevation view, and Figure-'3.

vention.

Figure 3 isa rear elevation view, and'Figure i 2 invention .'-is applied. Figure'fiis a plan view of a portion of this mechanism taken v.online "5- 5 ofFigure'B.

Figure G is a rear elevation view,and.iFigure"'l is ,a-is ide elevation view, of .still a differentftype *of direction finding equipmentembodying mylinvention.

. Figure 8 is a side elevation .view of another form of radio direction finding equipment 1117ilizing a modified type'of myinvention.

Figure 9 is a side elevation view ofstillia different embodiment of my invention in radio "direction finding equipment, and Figure 10 is a plan view of aportion of that device taken "on line' l 0-10 of Figure 9.

j: Figure 1'1 is a rear elevation iview,'and Figure L1 is aside elevation view, of still a difi'erent inogiifica'tionsof my invention in'airadi'o direction finder. Figure .13 is an inverted plan view er part of'the mechanism shown in Figure 12 taken along line l.3l3 of that figure, and Figure 14 is a view of a portion of the 'mechanism'online I l-" M of Figure '12.

i -While the radio direction finding equipment of my invention is valuablefor use'in'the'navigation of aircraft, I have illustrated in the drawings various types of installations particularly adapted for shipboard use. The sameprinciples would apply,'however, to aircraft radio direction :finding equipment. The term "craft as employed inthis specification, therefore, includes both'watercraft'and aircraft.

'- Direction finding radio "equipment-customarily employed ion'ship'board is generally one of three principal types. Inthe first type the loop or other directional antenna is supported directly from 'jand"depends below the radio receiver, such air-antenna I beingfshown in Figures '1 and 2 beneath the radio receiver I0. Theseeond type of installation, *shown'inFigu'res 3, 4, l1,=and 12, incorporates a loop antenna H directly associated with the'radio receiver l2, but having'an additional support, such as the base I3, mounted von'the roof of the cabin C. The third principal type of equipment'incorporates a radio receiver .mounted in some location remote from the loop iant "1a ll, 'shownin Figures "6., 7, 8 and9,whi'ch is a side elevation view, of a vdiflzerentform .of

radio direction. finding eguipment to which .my

ant na is supported "by a base 13 mounted on thereof of the cabin C, like'the antenna struc- ."ture'of Figures 3, 4, 11and'l2.

' In ieach type of conventional direction finding ,rad'io equipment the loop antenna is supported "forrotation about an upright axis, andan indicator is provided to designate .the rotative positfiitioiiof the antenna-relative to the centei'iline-or clude a plate l4 mounted on the bottom of the radio receiver 10, shown in Figures 1 and 2, which is graduated in degrees. Cooperating with this disk is an index pointer or indicator I5, located in a plane perpendicular to the plane of the loop. When the loop antenna l is disposed in a plane perpendicular to the longitudinal axis of the craft, as in the position of Figures 1 and'2, the pointer 15 will register with either the zero or the l80-degree mark on disk I4. As the direction of the loop Such indicator may inantenna is altered by swinging it about an upright axis, the amount of angular departure from the position shown in Figures 1 and 2 will be indicated by the pointer [5 on the graduated plate I4.

In the type of radio directionfinder shown in I line of the craft, just as in the case of the mechanism shown in Figures 1 and 2, as described above. In Figures 11 and 12 shaft !6 merely carries a head. l5, which preferably is circular, and has crosshairs on it corresponding to the pointer or pointers l5.

. In the form of mechanism shown in Figures ,6 and. '7 the loop antenna H is mounted in the same manner as that'shown in Figures 3 and fl,

and its shaft It carries a wheel I! which can .be turned to facilitate rotation or me antenna.

Inthis instance the disk l8, graduated in degrees, is mounted on the loop antenna support l3, and the pointer l9 cooperating with the dial I8 is geared to shaft l6 by gearing having .a one to one movement ratio. Again, therefore, when the plane of loop antenna H is perpendicular to the longitudinal axis of the craft, the pointer it will register with either the zero or the 180- degree graduation of the dial.

' The different locationsof the raolo receiving set and the types of loop antenna mounting described are conventional, but the application of my invention varles with the nature of such receiver and antenna installation. In. each in- .tance, however, the .principal requisite is that" the rotative axis of the loop antenna be aligned .with the bearing or rotative axisof the compass card of the crafts navigational compass, or that such rotative axes be correlated physically in some manner, such as by employing a mirrored reflection either of the loop antenna attitude indicator, or of the compass card, superimposed ings the loop antenna, its attitude indicator, and the compass card of the craftsnavigational compass all rotate about a commonaxis. Beferring particularly to the arrangementshown'in Fig- .ures 1 and 2, the antenna 1, the antenna at- 4 of the compass card, or of the casing 2, or both, relative to the common axis of rotation of the antenna I and of the compass card does not appreciably displace the compass cards rotative axis.

The mechanical correlation between the rotation of the loop antenna about its axis and the compass card may be effected by mounting on .the loop antenna an index member which cooperates with the card of the compass 2. While a single arrow closely overlying the compass and suspended from the antenna would serve as its attitude indicator index, in the mechanism shown in Figures 1 and 2 this index member is in the from of a-tube 3 which is carried by the loop antenna, such as being secured to its lower portion by a suitable clamp 30. This tube contains a light projected through a lens system to form an indicating pattern on the compass card, such, for example, as the bull's-eye 4|, shown in Figure 5. The lower end of this tube is disposed eccentrically of the common rotative axis of the loop antenna and the compass card, so that as the antenna is rotated its light pattern index will sweep the periphery of the compass card.

To locate the antenna attitude indicator in this manner the light tube may either be offset from the rotative axis of the antenna, or inclined relative to such axis, or both. The tube 3, as shown in Figure 2, is both inclined and offset. The degree of the tubes inclination may be adjusted as desired to locate the light projectionindex H in the proper position radially of the compass card by swinging the tube about pivot 3|, by which it is connected to the bracket 30. This pivot mounting of the tube also enables it to be swung upward out of the way into the inoperative position indicated in broken lines in, Figure 2, when it is desired to clear the space above the compass.

The construction ofthe compass 2- as illustrated in all of Figures 1 to 5 is standard, as is the base 29 and gimbal ring mounting 2|. The

. compass card 22 is pivoted at its center and is titude pointer I5, and the bearing. .fo r the card,

of the main ships compass 2, are in vertical alignment. Such alignment is maintained irrespective of the rolling or pitching movement of the ship, although the case of thecompa'ss' remains substantially level because it is supported from its base 20 by gimbal'ring's"'2l.' The tilt immersed in a liquid. As the heading of the "craft is altered the case of the compass is rotated relative to the compass card, and the lubber lines 23 move angularly around the card to indicate the change in heading of the craft. The fore and aft lubber lines are oriented in a direction parallel to thelongitudinal axis of the craft.

In the operation of my direction finding equipment the antenna I will be rotated about its axis until its planeis perpendicular to the bearing of the radio transmitting station on which the bearing is being taken, and the axis of the antenna loop is aligned with such station. Tube 3 will swing with the antenna to move the light pattern index 4| around the compass card 22. As

the antenna position is thus being established,

the correct bearing of the transmitting station will be indicated by the position of the antenna index on the compass card, irrespective of the disposition about such card of the compass case and lubber lines 23, and hence entirely irrespective of thejheading of the craft.

' Consequently it'is not at all necessary to know the heading of the craft in order to obtain bearings from it of several radio transmitting stations for establishing a fix of the crafts position, provided, of course, that the several bearings are taken-sufficiently quickly so that the craft has .not progressed along its course an appreciable distance meanwhile. Also the rolling, pitching or turning of the craft while the radio transmitsweats-s ting station "bearings are being determined does not in any-way aifect the bearing readings of the antenna attitude indicator M on the compass card, although if the heading of the craft changes, it-Willbe necessary to-tu-rn the antenna sufficiently to maintain its axis aligned with the transmitting stationwhen the compass bearing reading of such station is-beingtaken.

From the foregoing description of-the operation of my direction finder, it will beevident that the reading of aradio station-bearing does not depend at all'upon the heading of the craft.

Consequently, the-lubbers'lines 23 ofthecompass can be "totally ignored when taking "such readings, because they are of value onlyfo-r ascertainin'g the crafts heading. As "a matter of fact, I consider'a bull's-eye type of light-pattern index to be superior to -the-usual "lubbers line employed on a compass, and where my navigational device is installed, the .lubberslines 23,"

shown in Figure 5, may be omitted, provided that an index pointer and cooperating mari;,such that the loop antenna may be set withits axis parallel to the center line of the craft, are suppositicn'on-aradius of the compass "parallel tothe center line of the craft may be established'by placing the pointer l5, also carried by te'antenna I, in registry with the 'zero'graduation'oi plate I4. Thisplate, of course, is itself oriented properly with 'respect'to the center line :of the craft 'as previously explained. When-the loopantenna is fixed in that position, the bulls-eye light pattern will'be located as shownin solid lines in Figure 5.

If the antenna attitude index is to bra-employed only'for obtaining bearings of radio transmitting stations, it may be desired to'swing'the index supporting member, such as tube 3, into an inoperative position. Thus when such tube is swung about its pivot 3| to the broken line position illustrated in .Figure 2, the'space immediately above the compass'will be unobstructed.

While the proportions of the antenna attitude index mechanism shown inFiguresB and 4. are different from the device of Figures l and '2. the operation is the same. In this instance the shaft 15 carries the mounting tube 32 aligned with it. As before, the light tube 3 is secured to this .mounting by a, pivot'3l for swinging adjustment.

It is not necessary to describe the operation of thisstructure, because it is identical with -that of the mechanism shown in'Figures 1 and 2 and described previously. In order to swing the light tube from the solid line position to the broken line positionshownfin Figure 4,,however, in this instance .it.-.may be necessary to rotate the loop antenna H .sufficientlyso that the light tube will clear the window W in the cabin C whilebeing swung.

In the deviceof Figures 6 and '7, the light tube 3 again iscarried by a mounting tube 32, aligned with therotative axis of the loop antenna H. In this instance the wheel It! is added, but again the function .and operation of the antenna attitude index mechanism is exactly the same as I thatshown'in Figures 1 and and described above. "The only-difference 'in' thisnrrangement isthe location of the customary antenna atti'e tude reierence indicator 128, I9. When the usual lubbers lines are provided on the compass-such attitude indicator may be omitted. If "the light pattern projected 'by-the tube-3" is to be used in place'of the normal lubbers lines, however, for steeringthe craft, some antenna attitude "refer- "ence indicator, such'as 18 or '19, or some other mechanism must be providedto enable the loop antenna H to be fixed in a position in which its axis is parallel to the center line ofith'e-craft.

he device of Figure 8 does not have-anamtenna attitude 'indexmember which 'is supported in close proximityto the compass. In this instance, theface of thecompass 2 is illuminated indirectly by the light 24, so 'that'it is reflected in a convex mirror 33, mounted on the lower end of the antenna shaft 16 and generally per- -pendicular to it. On this mirror is a-ra'dial or diam-etral line, or diametral lines intersecting atright "angles, which maybe luminous if desired.

"The compass card is refiectedin the'mirror 33 and again in a fixed concave mirror 34, in which the antenna attitude index line or: lines is also reflected. The observer then sees the superimposedrefiections of the compass card and of "the antenna attitude indexline or'lines in mirror 34.

-'It is evident that any other 'systemof mirrors may be employed which'will superimpose images of the antenna attitude index and the compass card 7 The loop antenna arrangement-of Figure *9 '71s 'the sameas that oi-Figures 6J7 and-8, but'in this case the compass'z is not supported in a fixed position, but, on the contrary, 'its mounting 25 is connectedto the antenna mountingshaft 16 Ior'conjoint movement by a member 35. The compass is journaled in a bearing '26, aligned with the'antenna shaft [6, so that, as 'the 'antenna is rotated by wheel H, the compass case and lubbers lines 23 are also rotated. While in this instance the member interconnecting the compass and the antennais rigid, any connection which will coordinate the rotation of the antenna and of the compass mounting maybe used. In this embodiment of the invention the lubbers lines themselves constitute the index rotatable with the antenna to indicate 'its attitude relative to the compass card, instead of being fixed relative to the longitudinal axis of the craft. With this type of an arrangement it is essential that an indicator, such as IB,'be provided .to register the attitude of the antenna'relative to the crafts center line so that the lubbers lines may be set properly when the compass is to be used for reference in steering-the craft.

Vfith this m chanism. when tbebearing of a radio transmitting station is being determined, ijthe lubbers line adjacent to the antenna connecting member 35, which line maybe illuminated by a light 21 mounted on such connect- ;ing member, will cooperate with the compass -;c ard 22 to designatethe bearing ofthe trans- #mitting station, subject only to correction for compass variation. When it is desired to employ the compass 2 for determining the "heading of the craft, it will be necessary to place -the lubbers line adjacent to connecting member in a position parallel to the longitudinal axis the craft by aligning the pointer of indicator fHl atthe'zero graduation.

The form of direction finding equipment shown in Figure 9 is not preferred, however, because it is usually desirable to rotate the antenna l I rather rapidly, first in one direction and then inthe other, in order to position the loop with its axis directed at the transmitting station. The coincident oscillation of the casing of compass 2 creates some drag of the liquid in the compass case on the compass card 22, which will cause the compass card itself to oscillate somewhat. For that reason, it is very difiicult to obtain an accurate reading of the lubbers line on the compass card.

In the modification shown in Figures 11, 12, 13 and 14, like that of Figure 8, again there is no direct mechanical cooperation between the antenna attitude index and the compass card. In this arrangement a disk 36 is mounted on the lower end of the antenna ---shaft IS in a plane perpendicular to such shaft. This disk, as shown best in Figure 13, bears an appropriate index mark, such as a radial or diametral line, or two diametral lines perpendicular to each other, designated 31. One of these may have an arrow 31 corresponding to the direction of the loop when its axis is aligned with a radio transmitting station.

The compass 2 is of the customary type and is mounted in conventional style on the mounting 20. This mounting is extended upward somewhat, however, and carries a plane mirror 38, swingably supported upon pivot 39. This mirror is not silvered over its entire surface, as is evident from Figure 14, but a clear ring is left through which the compass card 22 is visible to the eye of the navigator. In the silvered portion of the mirror, located centrally and outwardly of the unsilvered portion, and to some extent in such unsilvered portion, an image of the antenna attitude index line 31, 31 will appear. Such image is superimposed upon the compass card in much the same manner as an arrow physically suspended from shaft l6 over the compass card and in close proximity to it would be.

As the loop antenna in the device of Figures 11 and 12 is rotated, the plate 35 and antenna attitude index 31, 31 will be rotated. The reflection of such index in mirror 38 will cooperate with the compass card in the same manner as the light pattern index 4| described in connection with the navigational device of Figures 1 and 2. Again, therefore, the actual compass rotation about an upright axis-coinciding with the rotative axis of the compass card of such compass, said mechanism comprising antenna attitude index means mounted on the loop antenna for rotation in synchronism therewith about the rotative axis of the antenna, and including means to project an antenna position index image onto the compass, said latter means comprising a light projection tube located immediately above the compass card and disposed-,eccentrically of such cards axis for cooperation with markings;

8 on the cards periphery, and said tube being mounted pivotally for swinging away from the compass when not being used.

2. Radio direction finding mechanism for correlating the attitude of a loop antenna with the compass card of a crafts navigational compass, comprising means supporting the loop antenna for rotation about an upright axis coinciding with the rotative axis of the compass card of such compass, antenna attitude index means including an index adapted to cooperate with the compass card, and means supporting said index means from the loop antenna for rotation in synchronism therewith, and for swinging about a generally horizontal axis between a position in which said index means are located immediately above the compass card and an inoperative position in which said index means are swung upwardly out of the region immediately above the compass. v

3. Radio direction finding mechanism for correlating the attitude of a loop antenna with the compass card of a crafts navigational compass, comprising means supporting the loop antenna for rotation about an upright axis coinciding with the rotative axis of the compass card of such compass, antenna attitude index means including a light pattern projection tube detached from the compass, and means supporting said tube from the loop antenna for rotation in synchronism therewith about the rotative axis of the antenna, to project the light pattern directly onto the compass card.

i. Radio direction finding mechanism for corwith the compass card of a crafts navigational compass, comprising means supporting the antenna for rotation about an upright axis coinciding with the rotative axis of the compass card of suchcompass, antenna attitude index means including a light pattern projection tube detached from the compass, and means supporting .said tube for rotation in synchronism with said antenna about its rotative axis, and inclined downwardly substantially from the rotative axis of the antenna to project the light pattern onto the periphery of the compass card.

5. Radio direction finding mechanism for correlating the attitude of a loop antenna with the compass card of a crafts navigational compass, comprising means supporting the loop antenna for rotation about an upright axis coinciding with the rotative axis of the compass card of .such compass, antenna attitude index means -its radio, directive antenna, comprising rotatable means mounted directly over, coaxially with, and detached from the crafts' compass and rotatable conjointly with the .antenna, said rotatable means including light index image projecting antenna-position index means, and means to effect superposition of an index image produced by said index means and the compass card in the sense that the compass card and index image may be viewed simultaneonsly in UNITED STATES PATENTS superimposed relationship. Number m Date 7. Radio direction finding mechanism as de- 733,910 Ladd July 14, 1903 fined in claim 6, in which the superpositioning 1,569 745 Hand Jan 12 1926 means comprises a light projection tube mount- 5 1 693051 Patterson 20, 1923 ed for swinging about an axis at an angle to the 1715:270 -m v May 28, 1929 axis of antenna rotation away from the com- 806,577 t May 19 1931 pass, from its lowered position wherein light 2 220 008 Woodward et aL Oct 29 1940 from said index means is projected through said 2246496 June 24 1941 tube directly onto the compass card to form 10 2253'430 Hunt aL 19, 1941 thereon the light image antenna-position index. schuhardt Jan 19, 1943 ROLLAND SABINS 2,326,337 Renzo Aug. 10, 1943 v REFERENCES CITED The following references are of record in the 15 file of this patent: 

